Patent GB-515635-A (GB)
Title: Improvements in or relating to hydraulic reciprocating pumps and motors
IPC: F01B3/00
Filed: 1938-06-08
Abstract: 515,635. Swash-plate pumps. CAREY, F. H. June 8, 1938, No. 17038. [Class 102 (i)] [Also in Group XXIX] In a hydraulic pump or motor utilizing a swash - plate mechanism, the shaftextends through the cylinder block and carries a ported disc valve controlling the passage of the working fluid from the valve casing to and from the rear ends of the cylinders and in front of the cylinder block carries a free floating swash-plate which is operatively associated with the ends of the pistons. The pump, Fig. 1, comprises a cylindrical block 1 with seven cylinders operated by a central shaft 3 housed in a ball bearing 5 in a thrust housing 6 bolted to the block 1 and carrying a mounting flange 7. The shaft passes through an oil seal and is splined at 11. The shaft carries an inclined inner race 12 for a double ball bearing which supports a swashplate 14 which carries a peripheral rib 15 which actuates the pistons. The swash-plate does not rotate with the shaft, but has a rotational creep due to friction. A head 17 with flared ports 18 closes the cylinder ends. A rotary disc valve 19 engages the head and is surrounded by a distance piece 20 which may be integral with the cylinder block 1 or end cover 21. The cover is provided with inlet and discharge passages 22, and a spring-pressed ball, relief valve leading back to the supply tank. The valve 19, Fig. 9, has an arcuate delivery passage 30 connected by a port 31 with an annular groove 32 in the edge of the valve and open to the discharge outlet. Never less than three cylinders deliver at once, so that there is little or no pulsation. Lost motion between the swash-plate rib 15 and the pistons is provided to prevent piston movement when both inlet and outlet are cut off. When lost motion is provided, the grooves may be 2/5 of a circle. This gives a shortened suction stroke. The areas of the valve and the annular cover area 35 are relieved to prevent friction losses. The relieved areas facilitate lubrication by the working fluid which for this purpose passes from area 35 through shaft bores 36, 37 to the swashplate chamber and returns by a spiral groove 34 in' the shaft to the valve. A non-reversible motor is shown in Fig. 11. There are nine cylinders to give a more even torque and the piston-stroke is longer than the pump piston stroke. The relief valve is omitted. The swashplate is more inclined and journalled to take a greater thrust, having a single ball-ring, arid a taper-roller bearing 40.. A balance weight 41 is provided. The ball thrust bearing 5, Fig. 1, is replaced by a taper roller-bearing 42. The piston ends are rounded to make frictional contact with the swash-plate. If the engine is to be reversible, the interior of the motor is maintained full of oil through a pipe 43 and the grooves 30, 27 in the valve are made of equal angular extent. In the valve Figs. 16 and 17 (not shown), the grooves 27, 30 are arranged at different pitch circles on either side of the circle, passing through the cylinder diameters, and each extends 180 degrees. In an alternative construction, the grooves 27, 30 are of the same diameter and length and extend less than 180 degrees, and the cylinders each have two ports on the same pitch circle. A modified swashplate pump mechanism similar to that shown in Fig. 11 is described wherein the plate carries a piston-operating rib.